The present invention relates to navigation and guidance of multiple aircraft when formation flying. The advantages of formation flight have long been known for fuel saving and defensive purposes. By flying in a V formation, aircraft can save fuel by flying behind the wing of a neighboring plane where there is less drag in an area of lower resistance. Military aircraft have been flown in formation for defensive purposes such as concentrated firepower in bomber formations and wingmen in fighter formations.
Commercial aircraft may also realize benefits by formation flying. The air cargo industry may benefit the most with overnight package delivery service aircraft flying in formation for fuel saving benefits. Another application for formation flying may be air traffic management. Air traffic controllers could use formation flying to optimize air space by parking aircraft in tight formations to save fuel while waiting to land.
However, formation flying is dangerous due to potential collisions between aircraft or an aircraft losing control due to disturbances in the air. Systems have been developed to reduce the risk of formation flying.
Station keeping is a method of maneuvering a follower aircraft to maintain a predetermined location relative to a leader aircraft for formation flying. Station keeping equipment (SKE) such as the AN/APN-169 is used on some US Air Force aircraft to enable aircraft to maintain formation positions by providing position error data. Position error data is obtained by converting SKE radar range and bearing measurements into along heading and cross heading positions and comparing these to desired heading positions.
When operating in a multiple aircraft formation, conventional station keeping equipment and relative positioning systems (such as GPS, TCAS, ADS-B) rely on independent, absolute positioning navigation systems in each aircraft or on single-measurement relative positioning means to assess the relative positions of all aircraft in the formation. These means do not have sufficient integrity or accuracy to safely fly in close formation with many aircraft. As a result, the formations are loosely flown and are subject to single-failure disruptions, as well as enemy detection, jamming and spoofing.
What is needed is an improved method of formation flying by obtaining robust, accurate and failure-tolerant relative bearing, distance and elevation information between a lead aircraft and each follower aircraft, and between each pair of follower aircraft.